Flexible display apparatus and manufacturing method thereof

ABSTRACT

A flexible display apparatus, including a flexible substrate including a bending area and a non-bending area; a display unit on the flexible substrate; and an encapsulation unit covering the display unit, the encapsulation unit including a first inorganic film, a second inorganic film, and an organic film between the first inorganic film and the second inorganic film, the organic film having a first thickness in the bending area and a second thickness greater than the first thickness in the non-bending area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/156,355, filed on May 17, 2016, which claims priority to and thebenefit of Korean Patent Application No. 10-2015-0100514, filed on Jul.15, 2015, in the Korean Intellectual Property Office, and entitled:“Flexible Display Apparatus and Manufacturing Method Thereof,” theentire contents of each of which are incorporated by reference herein intheir entirety.

BACKGROUND 1. Field

One or more exemplary embodiments relate to a flexible display apparatusand a manufacturing method thereof.

2. Description of the Related Art

Among display apparatuses, an organic light-emitting device may be anext-generation display apparatus, because organic light-emittingdevices may have fast response times as well as wide viewing angles andexcellent contrast.

SUMMARY

Embodiments may be realized by providing a flexible display apparatus,including a flexible substrate including a bending area and anon-bending area; a display unit on the flexible substrate; and anencapsulation unit covering the display unit, the encapsulation unitincluding a first inorganic film, a second inorganic film, and anorganic film between the first inorganic film and the second inorganicfilm, the organic film having a first thickness in the bending area anda second thickness greater than the first thickness in the non-bendingarea.

The non-bending area may include a first non-bending area and a secondnon-bending area, and the bending area may be between the firstnon-bending area and the second non-bending area.

The bending area may include a first bending area and a second bendingarea, and the non-bending area may be between the first bending area andthe second bending area.

The first bending area may have a first curvature, and the secondbending area may have a second curvature smaller than the firstcurvature.

The organic film in the first bending area may be thinner than theorganic film in the second bending area.

The organic film may be formed according to a liquid phase depositionprocess.

Embodiments may be realized by providing a manufacturing method of aflexible display apparatus, the method including providing a flexiblesubstrate including a bending area and a non-bending area; forming adisplay unit on the flexible substrate; forming a first inorganic filmcovering the display unit; forming an organic film on the firstinorganic film, the organic film having a first thickness in the bendingarea and a second thickness greater than the first thickness in thenon-bending area; and forming a second inorganic film on the organicfilm.

The non-bending area may include a first non-bending area and a secondnon-bending area, and the bending area may be between the firstnon-bending area and the second non-bending area.

The bending area may include a first bending area and a second bendingarea, and the non-bending area may be between the first bending area andthe second bending area.

The first bending area may have a first curvature, and the secondbending area may have a second curvature smaller than the firstcurvature.

The organic film in the first bending area may be thinner than theorganic film in the second bending area.

The organic film may be formed according to a liquid phase depositionprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates a schematic plan view of a flexible display apparatusaccording to an embodiment;

FIG. 2 illustrates a schematic side view of a bent structure of theflexible display apparatus of FIG. 1;

FIG. 3 illustrates a schematic cross-sectional view taken along a lineof FIG. 1;

FIG. 4 illustrates a schematic cross-sectional view of the inside of theflexible display apparatus of FIG. 1;

FIG. 5 illustrates a schematic plan view of a flexible display apparatusaccording to an embodiment;

FIG. 6 illustrates a schematic side view of a bent structure of theflexible display apparatus of FIG. 5; and

FIG. 7 illustrates a schematic cross-sectional view taken along a lineVII-VII′ of FIG. 5.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout.

It will be understood that although the terms “first”, “second”, etc.,may be used herein to describe various components, these componentsshould not be limited by these terms. These components are only used todistinguish one component from another.

It will be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orcomponents, but do not preclude the presence or addition of one or moreother features or components. It will be understood that when a layer,region, or component is referred to as being “formed on,” another layer,region, or component, it can be directly or indirectly formed on theother layer, region, or component. That is, for example, interveninglayers, regions, or components may be present. Further, it will beunderstood that when a layer is referred to as being “under” anotherlayer, it can be directly under, and one or more intervening layers mayalso be present. In addition, it will also be understood that when alayer is referred to as being “between” two layers, it can be the onlylayer between the two layers, or one or more intervening layers may alsobe present.

Sizes of elements in the drawings may be exaggerated for convenience ofexplanation. In other words, since sizes and thicknesses of componentsin the drawings are arbitrarily illustrated for convenience ofexplanation, the following embodiments are not limited thereto.

In the following examples, the x-axis, the y-axis and the z-axis are notlimited to three axes of the rectangular coordinate system, and may beinterpreted in a broader sense. For example, the x-axis, the y-axis, andthe z-axis may be perpendicular to one another, or may representdifferent directions that are not perpendicular to one another.

When a certain embodiment may be implemented differently, a specificprocess order may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list

FIG. 1 illustrates a schematic plan view of a flexible display apparatus1 according to an embodiment, FIG. 2 illustrates a schematic side viewof a bent structure of the flexible display apparatus 1 of FIG. 1, andFIG. 3 illustrates a schematic cross-sectional view taken along a lineof FIG. 1.

Referring to FIGS. 1 through 3, the flexible display apparatus 1according to an embodiment may include a flexible substrate 100 having abending area BA and a non-bending area NBA, a display unit 200 disposedon the flexible substrate 100, and an encapsulation unit 300. Theencapsulation unit 300 according to an embodiment may include a firstinorganic film 310, a second inorganic film 330, and an organic film 320disposed between the first inorganic film 310 and the second inorganicfilm 330.

The flexible substrate 100 may have a characteristic of flexibility andmay include various materials, for example, a metal or a plasticmaterial of polyethylene terephthalate (PET), polyethylene naphthalate(PEN), or polyimide. The flexible substrate 100 may include a displayarea DA corresponding to the display unit 200 and a peripheral area (PA)surrounding the display area DA.

The flexible substrate 100 may have the characteristic of flexibility,and the flexible substrate 100 may have a structure that is bendable andfoldable. In the present embodiment, the flexible substrate 100 may havethe bending area BA and the non-bending area NBA. As illustrated in FIG.1, the bending area BA may be between a first bending area BA1 and asecond bending area BA2. In the flexible display apparatus 1 accordingto the present embodiment, a first non-bending area NBA1 and a secondnon-bending area NBA2 may be arranged to face each other with respect toan axis in an extension direction of the bending area BA. FIG. 2illustrates, for example, the first non-bending area NBA1 and the secondnon-bending area NBA2 that may be parallel in a folded structure. Anangle formed by the first non-bending area NBA1 and the secondnon-bending area NBA2 may vary according to a bendable degree of thebending area BA.

The display unit 200 may be disposed on the flexible substrate 100. Thedisplay unit 200 may be disposed on an outer side or inner side of theflexible substrate 100.

Referring to FIG. 3, the display unit 200 may be disposed on theflexible substrate 100, and the display area DA may be an area in whichthe display unit 200 may be disposed. The display unit 200 may include aplurality of pixels and thin film transistors and capacitors (CAPs) tosupply signals to the respective pixels. The display unit 200 may be anorganic light-emitting display unit or a liquid crystal display unit.The present embodiment is a case in which the display unit 100 is anorganic light-emitting display unit.

The encapsulation unit 300 may include the first inorganic film 310, thesecond inorganic film 330, and the organic film 320 disposed between thefirst inorganic film 310 and the second inorganic film 320. Theencapsulation unit 300 may cover the display unit 200, and seal thedisplay unit 200 from external oxygen and moisture. The first inorganicfilm 310 and the second inorganic film 330 may be an inorganic compound,for example, silicon oxide or silicon nitride.

The organic film 320 disposed between the first inorganic film 310 andthe second organic film 330 may have a first thickness t1 in the bendingarea BA and a second thickness t2 in the non-bending area NBA. The firstthickness t1 of the organic film 320 may be less than the secondthickness t2 of the organic film 320. The second thickness t2 of theorganic film 320 disposed in the first and second non-bending areas NBA1and NBA2 may be thicker than the first thickness t1 of the organic film320 disposed in the bending area BA.

The organic film 320 may be formed by using a liquid phase depositionprocess, for example, an inkjet printing process. As described above,the organic film 320 may be formed to have the first and secondnon-bending areas NBA1 and NBA2 thicker than the bending area BA. Theorganic film 320 may be formed by controlling the amount of an organiccompound applied during a process of forming the organic film 320.

The organic film 320 may minimize stress at the bending area BA when theflexible display apparatus 1 according to an embodiment is bent orfolded at the bending area BA. When the flexible display apparatus 1 isbent, there may exist a neutral plane without stress since the tensileforce may be the same as the compression force inside the flexibledisplay apparatus 1. The stress inside the flexible display apparatus 1may increase according to a distance from the neutral plane. When astructure vulnerable to the stress is disposed above an upper side orbelow a lower side with respect to the neutral plane, the structure maybe exposed to continuing stress by receiving the tensile force and thecompression force. The stress applied to the structure may be reduced bypartially reducing the thickness of the flexible display apparatus 1,and moving the neutral plane to a position of the structure.

In the flexible display apparatus 1 according to an embodiment, athickness of the organic film 320 of the encapsulation unit 300 formedon the bending area BA may be partially adjusted. A position of theneutral plane may be controlled by forming the organic film 320 of theencapsulation unit 300 to be relatively thinner than in the first andsecond non-bending areas NBA1 and NBA2. A flexible display apparatus 1that may have minimized stress may be realized by disposing thestructure vulnerable to the stress on the neutral plane.

FIG. 4 illustrates a schematic cross-sectional view of the inside of thedisplay unit 200 of the flexible display apparatus 1 of FIG. 1.

The display unit 200 may include a plurality of pixels and the thin filmtransistors TFTs and CAPs electrically connected to the pixels to supplypower to the pixels. The display unit 200 may be an organiclight-emitting unit or a liquid crystal display unit. The presentembodiment is a case in which the display unit 200 is an organiclight-emitting unit. The thin film transistor TFT may include asemiconductor layer 202 including amorphous silicon, polycrystallinesilicon, or an organic semiconductor material, a gate electrode 204, asource electrode 206 s, and a drain electrode 206 d. A structure of thethin film transistor TFT will be explained in detail below.

First, a buffer layer 201 including silicon oxide or silicon nitride maybe disposed on the flexible substrate 100 to flatten a surface of theflexible substrate 100 and prevent introduction of impurities into thesemiconductor layer 202 of the thin film transistor TFT. Thesemiconductor layer 202 may be disposed on the buffer layer 201.

The gate electrode 204 may be disposed on the semiconductor layer 202,and the source electrode 206 s and the drain electrode 206 d may beelectrically connected to each other according to a signal applied tothe gate electrode 204. The gate electrode 204 may have adhesivenesswith an adjacent layer, a surface flatness of a stacked layer, andworkability, and may include a single layer or a multilayer includingone or more of aluminum (Al), platinum (Pt), palladium (Pd), silver(Ag), magnesium (Mg), Gold (Au), Nickel (Ni), Neodymium (Nd), iridium(Ir), Chromium (Cr), Lithium (Li), Calcium (Ca), molybdenum (Mo),titanium (Ti), tungsten (W), or copper (Cu).

A gate insulation film 203 including silicon oxide and/or siliconnitride may be disposed between the semiconductor layer 202 and the gateelectrode 204 to insulate the semiconductor layer 202 and the gateelectrode 204 from each other.

An interlayer insulation film 205 may be disposed on the gate electrode204. The interlayer insulation film 205 may include a single layer or amultilayer including a material, such as, silicon oxide or siliconnitride.

The source electrode 206 s and the drain electrode 206 d may be disposedon the interlayer insulation film 205. The source electrode 206 s andthe drain electrode 206 d may be electrically connected to thesemiconductor layer 202 through a contact hole formed in the interlayerinsulation film 205 and the gate insulation layer 203. The sourceelectrode 206 s and the drain electrode 206 d may have electricalconductivity and may include a single layer or a multilayer includingone or more of aluminum (Al), platinum (Pt), palladium (Pd), silver(Ag), magnesium (Mg), Gold (Au), Nickel (Ni), Neodymium (Nd), iridium(Ir), Chromium (Cr), Lithium (Li), Calcium (Ca), molybdenum (Mo),titanium (Ti), tungsten (W), or copper (Cu).

A protection layer may be formed to cover the thin film transistor TFTto protect the thin film transistor having the above-describedstructure. The protection layer may include an inorganic compound, suchas, silicon oxide, silicon nitride or silicon oxynitride.

A planarization film 207 may be disposed on the flexible substrate 100.The planarization film 207 may flatten an upper side of the thin filmtransistor TFT and protect the thin film transistor and variouscomponents when an organic light-emitting device is disposed on the thinfilm transistor TFT. The planarization film 207 may include anacryl-based organic compound or benzoncylobutene (BCB), for example. Asillustrated in FIG. 4, the buffer layer 201, the gate insulation layer203, the interlayer insulation layer 205, and the planarization film 207may be formed on the entire flexible substrate 100.

A pixel-defining film 208 may be disposed on the thin film transistorTFT. The pixel-defining film 208 may be disposed on the above-describedplanarization film 207 and may have an opening. The pixel-defining film208 may define a pixel area on the flexible substrate 100.

The pixel-defining film 208 may include an organic insulation film, forexample. The organic insulation film may include acrylic polymer such aspoly(methyl methacrylate) (PMMA), polystyrene (PS), a poly derivativehaving a phenol group, imide polymer, acryl ester-based polymer,amide-based polymer, fluorine-based polymer, p-xylene polymer, vinylalcohol polymer, or a mixture thereof.

An organic light-emitting device 240 may be disposed on thepixel-defining film 208. The organic light-emitting device 240 mayinclude a pixel electrode 210, an intermediate layer 220 including anemission layer EML, and an opposite electrode 230.

The pixel electrode 210 may be a (semi-)transparent electrode or areflective electrode. When the pixel electrode 210 is a(semi-)transparent electrode, the pixel electrode 210 may be, forexample, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide(ZnO), indium oxide (In₂O₃), indium gallium oxide (IGO), or aluminumzinc oxide (AZO). When the pixel electrode 210 is a reflectiveelectrode, the pixel electrode 210 may include a reflective layerhaving, for example, silver (Ag), magnesium (Mg), aluminum (Al),platinum (Pt), palladium (Pd), gold (Au), Nickel (Ni), Neodymium (Nd),Iridium (Ir), chromium (Cr), and/or a mixture thereof, and a layerhaving indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide(ZnO), indium oxide (In₂O₃), indium gallium oxide (IGO), or aluminumzinc oxide (AZO). In an embodiment, various materials may be usable, anda structure thereof may be variously changed to, for example, a singlelayer or a multilayer.

The intermediate layer 220 may be disposed on the pixel area defined bythe pixel-defining film 208. The intermediate layer 220 may include anemission layer EML that may emit light according to an electricalsignal. In addition to the emission layer EML, the intermediate layer220 may be, for example, a single layer or a complex structure includinga hole injection layer (HIL) disposed between the emission layer EML andthe pixel electrode 210, a hole transport layer (HTL), and an electrontransport layer (ETL) disposed between the emission layer (EML) and theopposite electrode 230, or an electron injection layer (EIL). In anembodiment, the intermediate layer 220 may have various structures.

The opposite electrode 230 covering the intermediate layer 220 includingthe emission layer EML and disposed opposite to the pixel electrode 210may be formed on the whole area of the flexible substrate 100. Theopposite electrode 230 may be a (semi-) transparent electrode or areflective electrode.

When the opposite electrode 230 includes a semi-transparent electrode,the opposite electrode 230 may include a metal layer having a low-workfunction, for example, lithium (Li), calcium (Ca), lithium fluoridecalcium (LiF/Ca), lithium fluoride aluminum (LiF/Al), aluminum (Al),silver (Ag), magnesium (Mg), and/or a mixture thereof, and a (semi-)transparent conductive layer of indium tin oxide (ITO), indium zincoxide (IZO), zinc oxide (ZnO), or indium oxide (In₂O₃). When theopposite electrode 230 includes a reflective electrode, the oppositeelectrode 230 may include a layer including lithium (Li), calcium (Ca),lithium fluoride calcium (LiF/Ca), lithium fluoride aluminum (LiF/Al),aluminum (Al), silver (Ag), magnesium (Mg), and/or a mixture thereof. Inan embodiment, a structure and a material of the opposite electrode 230may be changeable variously.

Referring to FIG. 4, the encapsulation unit 300 may be disposed on theflexible substrate 100 to cover the display unit 200. The encapsulationunit 300 may be a multilayer including at least one inorganic film andan organic film 320. The encapsulation unit 300 may effectively seal thedisplay unit 200 from oxygen and moisture from outside by including themultilayer. In the present embodiment, the encapsulation unit 300 mayinclude the first inorganic film 310, the second inorganic film 330, andthe organic film 320 disposed between the first inorganic film 310 andthe second inorganic film 330.

The first inorganic film 310 and the second inorganic film 330 mayinclude an inorganic compound and may include the same material ordifferent materials. The materials forming the first inorganic film 310and the second inorganic film 330 may be independent, for example, oneor more of silicon nitride, aluminum nitride, zirconium nitride,titanium nitride, hafnium nitride, tantalum nitride, silicon oxide,aluminum oxide, titanium oxide, tin oxide, cerium oxide, or siliconoxynitride (SiON).

The organic film 320 may include an organic compound and may include oneor more of acryl resin, methacrylic resin, polyisoprene, vinyl resin,epoxy resin, urethane resin, cellulose resin, or perylene resin. Theorganic film 320 may be formed by using a liquid phase depositionprocess, for example, an inkjet printing process.

FIG. 4 illustrates a cross-sectional view of the display unit 200including a boundary of the bending area BA and the non-bending areaNBA. As stated above, the organic film 320 may have the first thicknesst1 in the bending area BA and the second thickness t2 in the non-bendingarea NBA. The first thickness t1 of the organic film 320 in the bendingarea BA may be less than the second thickness t2 of the organic film 320in the non-bending area NBA. The flexible display apparatus 1 accordingto an embodiment may reduce, minimize, or eliminate stress applied tothe display unit 200 during bending and folding by partially adjusting athickness of the organic film 320 of the encapsulation unit 300. Theorganic film 320 in the bending area BA may be formed to be relativelythinner than the organic film 320 in the non-bending area NBA to controla position of the neutral plane inside the flexible display apparatus 1.The structure vulnerable to stress may be positioned on the neutralplane to realize a flexible display apparatus 1 that may have minimizedstress.

FIG. 5 illustrates a schematic plan view of a flexible display apparatus2 according to an embodiment, FIG. 6 illustrates a schematic side viewof a bent structure of the flexible display apparatus 2 of FIG. 5, andFIG. 7 illustrates a schematic cross-sectional view of the flexibledisplay apparatus 2 along a line VII-VII′ of FIG. 5. A display unit 200of the flexible display apparatus 2 illustrated in FIGS. 5 to 7 may havethe same structure as or a similar structure to the display unit 200 ofFIG. 4, and descriptions of the display unit 200 of FIGS. 5 to 7correspond to the descriptions of the display unit of FIG. 4.

Referring to FIGS. 5 to 7, the flexible display apparatus 2 according toan embodiment may include a flexible substrate 100, the display unit 200disposed on the flexible substrate 100 having a bending area BA and anon-bending area NBA, and an encapsulation unit 300. The encapsulationunit 300 according to an embodiment may include a first inorganic film310, a second inorganic film 330, and an organic film 320 disposedbetween the first inorganic film 310 and the second inorganic film 330.

The flexible substrate 100 may have a characteristic of flexibility andmay include various materials, for example, a metal material or aplastic material such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), or polyimide. The flexible substrate 100 may includea display area formed with the display unit 200 and a peripheral areadisposed to surround the display area.

The flexible substrate 100 may have a bendable or foldable structure dueto, for example, the flexible characteristic. In the present embodiment,the flexible substrate 100 may include a bending area BA and anon-bending area NBA, and the non-bending area NBA may be between afirst bending area BA1 and a second bending area BA2 as illustrated inFIG. 5. The flexible display apparatus 2 according to the presentembodiment may be bendable such that the first bending area BA1 and thesecond bending area BA2 have predetermined curvatures. As illustrated inFIG. 6, the first bending area BA1 may have a first curvature radius R1and the second bending BA2 may have a second curvature radius R2 greaterthan the first curvature radius R1. The first bending area BA1 may havea curvature greater than that of the second bending area BA2. In anembodiment, the first bending area BA1 and the second bending area BA2may have a same curvature.

The display unit 200 may be disposed on the flexible substrate 100. Thedisplay unit 200 may be disposed inside or outside the flexiblesubstrate 100.

Referring to FIG. 7, the display unit 200 may be disposed on theflexible substrate 100 and may be disposed in a display area DA. Thedisplay unit 200 may include a plurality of pixels and also include thinfilm transistors TFTs and CAPs to supply electrical power to therespective pixels. The display unit 200 may be an organic light-emittingdisplay unit or a liquid crystal display unit. The present embodiment isa case in which the display unit 200 is an organic light-emittingdisplay unit.

The encapsulation unit 300 may include the first inorganic film 310, thesecond inorganic film 330, and the organic film 320 disposed between thefirst inorganic film 310 and the second inorganic film 330. Theencapsulation unit 300 may cover the display unit 200 and seal thedisplay unit 200 from external oxygen and moisture. The first inorganicfilm 310 and the second inorganic film 330 may include an inorganiccompound, for example, silicon oxide or silicon nitride.

The organic film 320 disposed between the first inorganic film 310 andthe second inorganic film 3330 may have a thickness of the non-bendingarea NBA thicker than those of the bending areas BA1 and BA2. In thepresent embodiment, the first bending area BA1 may have a thirdthickness t3, the second bending area BA2 may have a fourth thicknesst4, and the non-bending area NBA may have a fifth thickness t5. Thethird and fourth thicknesses t3 and t4 of the organic film 320 in thebending areas BA1 and BA2 may be relatively less than the fifththickness t5 of the organic film 320 in the non-bending area NBA.

As describe above, the first bending area BA1 may have a first curvatureradius R1 and the second bending BA2 may have a second curvature radiusR2 greater than the first curvature radius R1, and the first bendingarea BA1 may have a curvature greater than that of the second bendingarea BA2. The organic film 320 disposed in the first bending area BA1may have the third thickness t3 less than the fourth thickness t4 of theorganic film 320 in the second bending area BA2.

The organic film 320 may be formed by using the liquid phase depositionprocess, for example, the inkjet printing process. A thickness of theorganic film 320 may be adjusted by controlling the amount of an organiccompound applied during forming the organic film 320.

The organic film 320 of the flexible display apparatus 2 according to anembodiment may minimize the stress in the bending areas BA1 and BA2 whenbeing bent or folded in the bending areas BA1 and BA2. When the flexibledisplay apparatus 2 is bent, there may exist a neutral plane withoutstress since the tensile force and the compression force may be sameinside the flexible display apparatus 2, and the stress in the flexibledisplay apparatus 2 may increase according to a distance from theneutral plane. When a structure vulnerable to the stress is disposed onan upper side or a lower side with respect to the neutral plane, thestructure may be exposed to continuing stress from the tensile force andthe compression force. The stress that may be applied to the structuremay be reduced when the neutral plane moves to a position of thestructure by partially adjusting a thickness of the flexible displayapparatus 2.

In the flexible display apparatus 2 according to an embodiment athickness of the organic film 320 of the encapsulation unit 300 formedon a bending area may be controlled. The organic film 320 in the bendingareas BA1 and BA2 may be relatively thinner than that of the non-bendingarea NBA to control a position of the neutral plane. By disposing thestructure vulnerable to the stress on the neutral plane, a flexibledisplay apparatus 2 having minimized stress may be realized.

Embodiments include the flexible display apparatus, which has beenexplained. Embodiments also include a manufacturing method of a flexibledisplay apparatus to manufacture such a flexible display apparatus.

Referring FIGS. 1 to 4, the method may include preparing the flexiblesubstrate 100 having the bending area BA and the non-bending area NBA.The flexible substrate 100 may have a flexible characteristic and mayinclude various materials, for example, a metal material or a plasticmaterial such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), or polyimide. In the present embodiment, the flexiblesubstrate 100 may include the bending area BA and the non-bending areaNBA, and the bending area BA may be disposed between the firstnon-bending area NBA1 and the second non-bending area NBA2 asillustrated in FIG. 1. FIG. 2 illustrates, for example, a structure inwhich the first non-bending area NBA1 and the second non-bending areaNBA2 may be disposed parallel to each other to form a folded structure.In an embodiment, it may be possible to change the structure to variousforms according to a bending degree of the bending area BA.

The method may include forming the display unit 200 on the flexiblesubstrate 100. The display unit 200 may be disposed inside or outside ofthe flexible substrate 100.

Referring to FIG. 4, various components of the display unit 200 of theflexible display apparatus 1 may be disposed on the flexible substrate100. Common layers, such as, the buffer layer 201, the gate insulationfilm 203, the interlayer insulation film 205, may be formed on theentire flexible substrate 100. After the buffer layer 201 is formed, apatterned semiconductor layer 202 may be formed on the buffer layer 201.The gate electrode 204, the source electrode 206 s, and the drainelectrode 207 d as components of the thin film transistor TFT may beformed together with the pattern semiconductor layer 202.

The planarization film 207 having a flat upper surface may be formed onthe entire flexible substrate 100 to cover the thin film transistor TFT.A patterned pixel electrode 210 may be formed on the planarization film207. The pixel electrode 210 may be electrically connected to the thinfilm transistor TFT through a via hole formed in the planarization film207. Thereafter, the pixel-defining film 208 may be formed to expose acenter portion of the pixel electrode 210 and to cover a boundaryportion of the pixel electrode 210. The pixel-defining film 208 maydefine the pixel area. The intermediate layer 220 including alight-emitting layer may be formed in the pixel area defined by thepixel-defining film 208. The intermediate layer 220 may have one layeras a common layer to partially correspond to the flexible substrate 100or the other layer as a patterned layer patterned to correspond to thepixel electrode 210. Thereafter, the opposite electrode 230 may bedisposed on the entire flexible substrate 100.

Now referring to FIGS. 3 and 4, the encapsulation unit 300 may be formedon an upper side of the opposite electrode 230. In the drawings, theencapsulation unit 300 is illustrated as, for example, directly formedon the encapsulation unit 300. In an embodiment, a functional layer,such as, a capping layer (CLP), may be formed on the opposite electrode230 and then the encapsulation unit 300 may be formed thereon.

First, the first inorganic film 310 may be formed on the oppositeelectrode 230. Thereafter, the organic film 320 may be formed on thefirst inorganic film 310. The organic film 320 may be formed by usingthe liquid phase deposition process, for example, the inkjet printingprocess. The second inorganic film 330 may be formed on the organic film320. The first inorganic film 310 and the second inorganic film 330 mayinclude an inorganic compound, for example, silicon oxide or siliconnitride. The encapsulation unit 300 may include a multilayer having atleast one inorganic film and the organic film 320. The encapsulationunit 300 having such a structure may seal the display unit 200 fromexternal oxygen and moisture.

The organic film 320 disposed between the first inorganic film 310 andthe second inorganic film 330 may have the first thickness t1 in thebending area BA and the second thickness t2 in the first and secondnon-bending areas NBA1 and NBA2. The first thickness t1 of the organicfilm 320 may be thinner than the second thickness. The second thicknesst2 of the organic film 320 in the first and second non-bending areasNBA1 and NBA2 may be thicker that the first thickness t1 of the organicfilm 320 in the bending area BA. The organic film 320 may have athickness in the first and second non-bending areas NBA1 and NBA2relatively thicker than the bending area BA by adjusting the amount ofthe organic compound when the organic film 320 may be formed.

The organic film 320 of the flexible display apparatus 1 according to anembodiment may minimize the stress in the bending area BA when beingbent or folded in the bending area BA. When the flexible displayapparatus 1 is bent, there may exist a neutral plane without stresssince the tensile force and the compression force may be same inside theflexible display apparatus 1, and the stress in the flexible displayapparatus 1 may increase according to a distance from the neutral plane.When a structure vulnerable to the stress is disposed on an upper sideor a lower side with respect to the neutral plane, the structure may beexposed to continuing stress from the tensile force and the compressionforce. The stress that may be applied to the structure may be reducedwhen the neutral plane moves to a position of the structure by partiallyadjusting a thickness of the flexible display apparatus 1.

In the flexible display apparatus 1 according to an embodiment athickness of the organic film 320 of the encapsulation unit 300 formedin the bending area BA may be partially adjusted. A position of theneutral plane may be controlled by forming the organic film 320 in thebending area BA to be relatively thinner than in the first and secondnon-bending areas NBA1 and BNA2. A flexible display apparatus 1 that mayhave minimized stress may be realized by displacing the structurevulnerable to the stress on the neutral plane.

By way of summation and review, an organic light-emitting device mayinclude thin film transistors and organic light-emitting elements formedon a substrate, and the organic light-emitting elements themselves mayemit light. The organic light-emitting device may be used as a displayunit of a small product, such as, a mobile phone, or a large product,such as, a television.

A flexible display apparatus may include a flexible substrate includinga material, such as, a resin composite, rather than a comparative glasssubstrate to have flexibility. Mechanical damage to a layer disposed ina bending area of a flexible display apparatus may occur, due to, forexample, stress applied to the bending area while bending the flexibledisplay apparatus.

One or more exemplary embodiments relate to a flexible display apparatusthat may have reduced stress inside the flexible display apparatusduring bending and a manufacturing method thereof.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of skill in the art as of thefiling of the present application, features, characteristics, and/orelements described in connection with a particular embodiment may beused singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. A display apparatus, comprising: a substrateincluding a bending area and a non-bending area; a display unit on thesubstrate; and an encapsulation unit covering the display unit, theencapsulation unit including a first inorganic film, a second inorganicfilm, and an organic film between the first inorganic film and thesecond inorganic film, the organic film having a first thickness in thebending area and a second thickness greater than the first thickness inthe non-bending area.
 2. The display apparatus as claimed in claim 1,wherein: the non-bending area includes a first non-bending area and asecond non-bending area, and the bending area is between the firstnon-bending area and the second non-bending area.
 3. The displayapparatus as claimed in claim 1, wherein: the bending area includes afirst bending area and a second bending area, and the non-bending areais between the first bending area and the second bending area.
 4. Thedisplay apparatus as claimed in claim 3, wherein: the first bending areahas a first curvature, and the second bending area has a secondcurvature smaller than the first curvature.
 5. The display apparatus asclaimed in claim 4, wherein the organic film in the first bending areais thinner than the organic film in the second bending area.
 6. Thedisplay apparatus as claimed in claim 1, wherein the organic film isformed according to a liquid phase deposition process.
 7. Amanufacturing method of a display apparatus, the manufacturing methodcomprising: providing a substrate including a bending area and anon-bending area; forming a display unit on the substrate; forming afirst inorganic film covering the display unit; forming an organic filmon the first inorganic film, the organic film having a first thicknessin the bending area and a second thickness greater than the firstthickness in the non-bending area; and forming a second inorganic filmon the organic film.
 8. The manufacturing method as claimed in claim 7,wherein: the non-bending area includes a first non-bending area and asecond non-bending area, and the bending area is between the firstnon-bending area and the second non-bending area.
 9. The manufacturingmethod as claimed in claim 7, wherein: the bending area includes a firstbending area and a second bending area, and the non-bending area isbetween the first bending area and the second bending area.
 10. Themanufacturing method as claimed in claim 9, wherein: the first bendingarea has a first curvature, and the second bending area has a secondcurvature smaller than the first curvature.
 11. The manufacturing methodas claimed in claim 10, wherein the organic film in the first bendingarea is thinner than the organic film in the second bending area. 12.The manufacturing method as claimed in claim 7, wherein the organic filmis formed according to a liquid phase deposition process.
 13. A displayapparatus, comprising: a substrate including a bending area and anon-bending area; a display unit on the substrate; and an encapsulationunit covering the display unit, the encapsulation unit including a firstinorganic film, a second inorganic film, and an organic film between thefirst inorganic film and the second inorganic film, the organic filmhaving a first thickness in the bending area and a second thicknessgreater than the first thickness in the non-bending area, and the firstthickness of the organic film corresponding to the bending area issubstantially constant.
 14. The display apparatus as claimed in claim13, wherein: the non-bending area includes a first non-bending area anda second non-bending area, and the bending area is between the firstnon-bending area and the second non-bending area.
 15. The displayapparatus as claimed in claim 13, wherein: the bending area includes afirst bending area and a second bending area, and the non-bending areais between the first bending area and the second bending area.
 16. Thedisplay apparatus as claimed in claim 15, wherein: the first bendingarea has a first curvature, and the second bending area has a secondcurvature smaller than the first curvature.
 17. The display apparatus asclaimed in claim 16, wherein the organic film in the first bending areais thinner than the organic film in the second bending area.
 18. Thedisplay apparatus as claimed in claim 13, wherein the organic film isformed according to a liquid phase deposition process.